Why Your Pool Filter is Turning Red and What to do

Pool filters are supposed to be the device that keeps your pool as one of the most beautiful spots on your property. But, when it begins to turn red, you might grow concerned. Fortunately, this is a relatively common occurrence, and there are solutions available to resolve this issue.

When your pool filter turns red, it is likely that there is a presence of either one or various minerals in your pool’s water. To remove the red color and ultimately, the unnecessary minerals, you need to figure out their source, test for what types of minerals are present, and add a metal remover. 

Lucky for you, you do not need to start tearing down your pool to get to the source of your red filter problem. Metal being present in water is a common problem and one that can be fixed within a few days. There is no need to drain your pool or totally gut your filter! You will likely want to stay out of the pool while you complete the process, but it is not overly complicated other than that. Continue reading to figure out the causes behind a red filter and how to remove the red tint from it. 

What Causes Pool Filters to Turn Red? 

There is nothing better than a cast iron skillet that has a thick cut of meat on it and is sizzling those sides to perfection. Even better, have you ever seen a beautiful copper tub that looks so inviting you could likely just move in and call yourself a fish for the rest of your life? Iron, copper, and other metals all have their place in this world, but when it comes to your pool water, there is no room for them whatsoever.

If your filter has begun to turn red or is completely red already, it is likely that there are metals present in your water. Tiny micro metals that are found in the water can turn the filter red and cause you to panic. These are most typically iron, copper, or another common type of metal.

Of course, telling you that the problem is relatively common and then simultaneously telling you that you have metal in your pool water can be slightly concerning. However, stick with me. Fortunately, because this problem comes up in pools all across the nation, common solutions have been developed that can help you get back to a clean, crisp filter and pool. 

This might still leave you wondering how metal gets into your pool’s water in the first place- which we will address in just a moment. However, keep in mind that the sooner you address the issue, the more easily the resolution will be, and the quicker you can get back to enjoying a hot summer’s day with your friends and family in your pristine backyard pool.

How Does Metal Get Into Your Pool’s Water? 

Metals exist in all water, but what matters is how much metal there is present within the water that your pool is using. Largely, the location that you live can have a lot to do with the concentration of metal in your water. Or, if you are using well water to supply water for your home, you might notice an increase in iron from the well, for example.

When it comes to pool water, there are a few common sources for metal that you will find. Once you nail down the source, you will be able to better treat your red filter problem. A few sources include the pool heater, algaecide, and the original source of water for your pool (and often, home).

Let’s take a closer look at the sources that allow metal to get into your poo’s water.

Pool Heater 

For those of you that do not have a pool heater, go ahead and skip along to the other possibilities because this section will be a waste of your time. For those of you that do have a heater though, sit tight. And, for those of you who do not have a pool heater but are now curious about the luxury that this can provide, stay tuned for important things to remember about pool heater installation.

Your pool heater has a copper heat exchanger in it that, over time, can break down. I know, this is shocking news for those of you that though your heater could go on and on forever, but it can’t. And, once it starts to break down, you will have plenty of issues. Typically, though, there are plenty of solutions to be able to keep your pool heater functional by replacing minor parts. 

Aside from your heater slowly falling apart, the copper heat exchanger can break down. This is typically caused by poor chemical balances in your pool which thus causes the metal to break off into your pool. I hate to break it to you, but do not go blaming your heater because the breakdown is ultimately your own fault. 

One of the main reasons that the copper heat exchanger can break down is due to poor pool maintenance that allows the chemical imbalance to occur. You have to stay on top of your pool’s chemical balance to ensure that all contributing parts stay well maintained and high-functioning- including the pool heater.

If the copper heat exchanger does begin to break down, you will find small bits of copper in your pool. However, you likely will not see these floating around aimlessly. Instead, you will see this show up as a bright red color on your pool filter as it collects the excess metal that is not supposed to be in the water.


Algaecide is a great tool to get all that gunky algae out of your pool. Algae grow in so many pools and other locations, and it is just as ugly (if not uglier) of a problem as metal. However, when you use algaecide, there is copper present in the product that helps to kill algae. 

If chemicals in your water are out of balance, the extra metals can cause your filter to turn a bit red or create a red tone in the pool water itself. Again, this comes back to maintaining a chemical balance within your pool. If you are using too much algaecide, or if you are not maintaining your pool’s chemicals while using algaecide (or in general), you might begin to see the collected residual pieces of metal as a bright red color on your pool filter.

Water Source 

Outside of the pool and various chemicals and tools added to your pool, you might want to consider the source of your water as to how the metal gets into your pool water in the first place.. If you are living in an area that requires you to use well water, this could be your culprit.

Now, using well water is going to be something that will cause metal to be in your water for as long as you use it, so this is going to be a continuing problem. However, it can be managed and you do not have to worry about red filters for the entirety of your pool’s existence. You will just need to pay special attention and realize that the source of your water (a source that is high in mineral and metal content) will require additional maintenance work on your pool.

How to Remove Metal From Your Pool Water and Fix a Red Pool Filter

Metal present in your water does not have to be an ongoing issue. With the proper treatment, it can be gone and the red in your water and filter can be distinguished in no time at all. There are a few steps you are going to have to take in order to get rid of it, but ultimately, the process is easy and only requires a few gizmos and gadgets of modern technology to get your water and filter back to glistening blues and whites. 

To remove metal from your pool water and fix a red pool filter, consider the following steps:

  1. Test the pool water to determine the type of metals that are present in it. This is important because there are different treatments for different metals. You can either purchase a test kit that you can perform yourself or you can take a water sample into your local pool store and get the water tested from them. 

Either step is quite easy and accurate, so it comes to a matter of personal choice and what is most convenient for you. However, performing the test is necessary to determine what type of metal is in your pool’s water and then tracing this back to its source for treatment.

  1. Treat the water with a specific metal remover. After you have figured out the metals present you will need to treat your water with a metal remover. If your filter is red, it is highly likely that the metals are iron, copper, or manganese. 

Be sure to read the instructions for whichever metal remover you are using to ensure that you have added it the correct way to your water. Metal removers can be purchased at any pool store or you can even grab them online. 

  1. Allow the pump and filter to run for at least 12 hours. If you can afford more time, it would be even better to run it for 24 hours. After this, the redness in your filter should begin to go away, and you should be able to tell a noticeable difference. 

If it is going slowly, allow your pump and filter to run a bit longer to make sure all the water has gone through. Avoid entering the pool during this time so that you are not in contact with the metal remover.

  1. Turn the filter off and brush down the walls and floor of your pool and then leave the pump and filter on for another 12-24 hours. Once that is done, you can vacuum your pool to waste and get all the remaining gunk out of your pool. If you are using well water or have a constant source of metal in your pool, you’ll likely have to use metal remover in your weekly maintenance routine. 

Jed Arnold

Jed spent every year from the ages of 15 - 22 as a Lifeguard (Red Cross) and ages of 17 - 22 as a Certified Pool Operator (CPO). Between working for over a dozen facilities and owning a pool, he carries over a decade of pool experience.

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